The present invention relates generally to excimer lamps (xe2x80x9cexcilampxe2x80x9d), and particularly to high power, high efficiency excimer lamps.
Pulsed flashlamps providing intense emission of discharge plasma are discussed by Yu. G. Basov in Pumping sources for microsecond lasers, 1990, p.88-118. These flashlamps comprise a transparent outer casing, electrodes and power supply. Switching elements used in the power supply limit specific electric power deposited into gas discharge and pulse repetition rate. Hence the flash-lamp average radiation power is limited. Besides, the electrode material and outer casing are damaged at high input power resulting in high probability of flashlamp damage due to strong mechanical stress appearing during pumping pulse.
A cylindrical source of CW ultraviolet radiation is discussed by A. P. Golovitsky, and S. N. Kan in Optika i Spektroskopoya, 1993, vol.75, No.3, p.603-607. The source comprises pipe-shaped electrodes attached to the ends of transparent dielectric tube filled with gas, cooling system and power supply. Disadvantages of this source are nonuniformity of the radiation intensity along its length and complex cooling system such that only the cathode is water cooled while the tube itself remains uncooled.
U.S. Pat. No. 3,721,851 (Coaxial Flash-Lamp, class H 01 J 61/30, issued Mar. 20, 1973) discloses a coaxial flash-lamp which comprises two coaxial dielectric tubes forming circular discharge cavity and two coaxial conductors, one of which is placed on the inner surface of the inner tube. Circular electrodes connected with inner and outer conductors are placed in the coaxial cavity.
Possibilities for the application of high-efficiency, high-output excilamps operating at wavelengths below 250 nm range from waste treatment to materials processing. In waste treatment, conventional ultraviolet oxidation technology is used. UV light at wavelengths below 250 nm generates oxidizing species in aqueous effluent that contain traces of organic contaminants. An oxidant such as hydrogen peroxide usually is added to the wastewater, where it is dissociated by UV photons to produce strongly oxidizing OH radicals that are capable of completely oxidizing many organic compounds in a stepwise fashion (in complete mineralization, all carbon atoms are oxidized to CO2, hydrogen atoms are oxidized to H2O, and other nonmetallic elements to corresponding anions). Unfortunately, conventional UV sources, such as mercury or xenon lamps, do not emit efficiently or continuously at wavelengths below 240 nm, so there are opportunities to improve the destruction efficiency of this process with the application of one or more excilamp sources. The high-intensity light from excilamps also is expected to directly excite organic compounds, thus increasing their reactivity and hence their susceptibility to oxidation This also will be valuable as a means of completely destroying the most refractory organic contaminants, and even increasing maximum concentrations of organic contaminants treatable by the UV oxidation process. Complete mineralization of toxic organic compounds is a key objective in the treatment of contaminated wastewater.
In view of all of the above, there is a need for a high intensity, high efficiency excilamp source of UV light.
An object of the claimed invention is to improve average optical radiation power of glow discharge lamps which is achieved by the following way. According to the invention, a powerful glow discharge lamp comprises two coaxial tubes (inner and outer), the outer tube being optically transparent, with electrodes (cathode and anode) attached at the tubes"" ends; working gas fills the cavity between the inner and outer tubes; the electrodes are made as coaxial cylindrical tumblers placed, respectively, on the ends of the inner and outer tubes in such a way that one end of the cathode is inserted into the inner tube, while the anode coaxially covers the outer tube and the inner tube is extended through the anode. The glow discharge lamp further comprises a cooling liquid tube coaxially located within the inner tube. Cooling fluid flows within the cooling liquid tube, and exits through holes in the side surface of the cooling liquid tube into the cavity cathode. The cooling fluid removes heat from the cathode and flows through the inner tube from which it subsequently exits. The cooling fluid also removes heat from the inner tube surface as it flows along the inner tube. The glow discharge lamp further comprises a circumferential heat extracting radiator in physical contact with the anode from which it removes heat.